1. Field of the Invention
This invention relates to the abrasive finishing of optical quality lenses particularly regarding fining operations in the manufacture of eyeglasses.
2. Description of the Prior Art
In the past, opthalmic lenses were prepared by employing the action of abrading tools, usually of cast iron, on the lens blank in the environment of an abrasive slurry. Commonly, the abrading tool was abraded as well as the lens blank. As the operation progressed, the tooling became more defective and resultant lens became more imperfect. Costly and time consuming tool retruing was continually required. Replaceable tool facings made of materials capable of adhering and conforming to the tool face came into use for the purpose of protecting the tooling from the abrasive effects of the slurry and the lens surfacing operations. The facings permitted the curvature of the tool to be translated to the lens blank by means of the action of the abrasive slurry between the tool facing and the lens blank.
Currently used tool facings do not give indication of the amount and character of wear effects on the facing as abrasive operations progress. The result, again, is frequently damage to expensive tooling, time consuming corrective action, and imperfect lens products.
Additionally in the past, whether the surfacing tool was used with or without a facing, irregular slurry flow patterns between the tool or facing and the lens blank contributed to particular tool and facing wear problems which were translated into an imperfect lens surface. Complete absence of or inadeqate slurry flow and availability of abrasive material adversely affected abrasive action and created dry or hot spots attributable to the lack of cooling affect associated with slurry flow.
The present invention overcomes the above mentioned problems by providing a replaceable lens surfacing pad with an integral wear indicating pattern which will clearly reveal amounts and irregularities of wear to the pad before tooling damage occurs. The wear pattern further makes the working surface of the pad contacting the lens blank more accessible to slurry, thus improving slurry flow and resulting in fresh abrasive particle availability and the desired cooling affects.